As a method of forming a circuit pattern on a semiconductor wafer, the following method and the like have been employed. A semiconductor wafer is coated with a coating material called a resist; an exposure mask (reticle) of a circuit pattern is laminated on the resist; visible light, ultraviolet light, or an electron beam is irradiated thereon; the resist is exposed for development to form a circuit pattern by the resist on the semiconductor wafer; and the semiconductor wafer is etched using the circuit pattern of the resist as a mask.
When designing and manufacturing a semiconductor device, dust management in a manufacturing device such as an exposing/etching device and evaluation of a circuit pattern shape formed on a wafer are important, and an inspection and measurement are performed by an optical or SEM (Scanning Electron Microscope)-type imaging device. As an optical imaging device, an optical defect inspection device in which defects are detected by illuminating a laser beam onto a wafer to observe scattered light from defects in the dark field of view, or an optical appearance inspection device in which the positions of defects are specified on the basis of an optical image in the bright field of view detected by irradiating a lamp beam or laser beam is known (for example, Japanese Patent Application Laid-Open No. H7-270144 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2000-352697 (Patent Document 2)). As an SEM-type imaging device, a CD-SEM (Critical Dimension Scanning Electron Microscope), or a DR-SEM (Defect Review Scanning Electron Microscope) is known (for example, Japanese Patent Application Laid-Open No. 2007-250528 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2010-087322 (Patent Document 4)). Further, a scanning charged particle microscope such as an SIM (Scanning Ion Microscope) or an STEM (Scanning Transmission Electron Microscope) is used in some cases.
As circuit pattern evaluation methods in, for example, the CD-SEM among the imaging devices, there are (1) a method of measuring dimensions such as the width of a line pattern and the diameter of a contact hole so-called CD values, (2) a method of calculating the amount of characteristics of an image that is high in correlation with a pattern shape, and (3) a method of detecting the two-dimensional outline of a patter from an SEM image of a circuit pattern (hereinafter, referred to as an evaluation pattern) to be evaluated. In order to stably perform the evaluation with a high degree of accuracy, it is necessary to obtain a high-magnification and high definition SEM image using the CD-SEM. Specifically, it is required to match the field of view to an arbitrary evaluation pattern on a wafer at hundreds of thousands of magnifications, and to adjust the focus position of a converged electron beam to be irradiated to the surface of the wafer. An imaging sequence including the movement of the field of view and the image quality adjustment is designated using a file called an imaging recipe. Once the imaging recipe is produced, the same kind of wafer can be automatically imaged by the CD-SEM without special operations by an operator.
In order to image and evaluate fine circuit patterns in the imaging device represented by the CD-SEM, it is necessary to perform global alignment (detection of position shift and detection of rotation of a wafer) of a wafer. In the global alignment, patterns on a wafer whose coordinates are already known are imaged at a few positions as alignment patterns, and the imaged images and a preliminarily-prepared image (hereinafter, referred to as a “template” or “matching data” of an alignment pattern) of an alignment pattern are matched to each other, so that the position shift and the rotation of the wafer are detected. An optical microscope is used to image the alignment pattern.